Preheat oven to 200C/400F.
Add the buttercup squash, carrots, onion, and garlic to a roasting pan. Drizzle the veggies with olive oil and maple syrup. Season the veggies with salt and pepper, to taste.
Roast the vegetables for 25 minutes, or until tender.
Transfer the vegetables to a large pot and add the vegetable broth, heavy cream, cinnamon, and nutmeg. Simmer for 5-10 minutes then puree with an immersion blender.
Serve soup warm.